In sewing corners with a two-needle sewing machine, in known fashion the inner corner is worked on, after stitch formation the needle which produces the inner seam is inactivated, the outer needle continues to sew into the outer corner, and the machine is disengaged with the outer needle in the down position. After the workpiece is rotated into the new sewing direction, sewing is continued with the outer needle until it comes opposite the inner (corner point, then the inner needle is activated again.
In U.S. Pat. No. 4,526,114, such a method is illustrated and described. According to U.S. Pat. No. 4,526,114 when working on the inner corner the outer and inner needles execute stitches in tandem on the workpiece, when the inner needle executes a shortened stitch to form the corner stitch, the outer needle also executes an identical shortened stitch. In the great majority of cases, this shortening of stitches is required, in order to be able to end the stitching exactly at the predetermined point of the inner seam. The short stitch in the outer seam causes distortion of the entire seam formation. A shortened stitch is only acceptable in the corner region.
A short stitch within a seam structure is undesireable and lowers the quality of the product.